Variable-geometry fan and method for control thereof

ABSTRACT

A variable-geometry fan, for cooling the lubricant of an internal-combustion engine includes a hub bearing a ring of blades having an elastically deformable structure and incorporating laminas made of a shape-memory alloy. The application of thermal energy to the laminas, so as to vary the geometry of the blades, envisages circulation of a hot fluid and of a cold fluid through internal ducts of the blades.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Italian Application NumberTO2011A000986 filed on Oct. 28, 2011, the entire disclosure of which isincorporated by reference

FIELD OF THE INVENTION

The present invention relates to cooling fans, in particular, albeit notexclusively, for cooling the lubricant of internal-combustion engines ofindustrial vehicles and the like.

Fans of this sort traditionally comprise a rotating hub bearing a ringof blades: in order to regulate the flow of air generated in use by thefan, so as to guarantee optimal cooling conditions, it is known tomodify the geometrical configuration of the blades.

PRIOR ART

The European patent application No. EP-2078865A2 filed in the name ofthe present applicant describes a variable-geometry fan in which theconfiguration, of the blades is varied with the use of a shape-memorymaterial. More in particular, each blade of the fan has an elasticallydeformable structure incorporating at least one lamina made of ashape-memory metal alloy designed to be heated to modify the profile ofthe blade and thus regulate the flow of air produced by the fan, evenkeeping the speed of rotation thereof unaltered. Heating of the laminasmade of shape-memory alloy is obtained by the Joule effect, i.e., viathe supply of appropriately controlled electric current through thelaminas themselves.

This solution, albeit altogether satisfactory and effective, in certainapplications could be improved further in terms of rapidity andpromptness of variation of the geometry, in particular as regardsrestoration of the original configuration of the blades, i.e., theconfiguration prior to heating of the shape-memory laminas.

SUMMARY OF THE INVENTION

According to the invention, the above object is achieved via avariable-geometry fan of the type defined in the pre-characterizing partof Claim 1, the peculiar characteristic of which lies in the fact thatthe control means for applying thermal energy to the laminas made ofshape-memory alloy of the blades so as to vary the geometry thereofinclude a circuit for circulation of a thermal fluid through internalchannels of each blade.

According to the invention, the circulation circuit includes a firstdelivery and return line for a hot liquid, a second delivery and returnline for a cold liquid, and respective solenoid valves driven by anelectronic control unit as a function of the temperature of the enginelubricant to which the fan is to be operatively associated.

-   -   a. The electronic control unit can be programmed so as to drive        the two solenoid valves according to different logics as a        function of the need of use of the fan.    -   b. Yet a further object of the invention is a method for        controlling the geometry of the blades of the variable-geometry        fan.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail with reference to theannexed drawings, which are provided purely by way of non-limitingexample and in which:

FIG. 1 is a schematic perspective view of a variable-geometry fanaccording to the invention;

FIG. 2 shows the electro-hydraulic scheme of the control system of thefan;

FIG. 3 shows a detail of FIG. 1 at a larger scale;

FIGS. 4 and 5 are two perspective views that show respective componentsof FIG. 3;

FIG. 6 is a schematic front perspective view of one of the blades of thefan;

FIG. 7 is a cross-sectional view at a larger scale according to the lineVII-VII of FIG. 6;

FIG. 8 is a perspective view at a larger scale sectioned according toline VIII-VIII of FIG. 3;

FIG. 9 shows a variant of FIG. 8; and

FIGS. 10, 11 and 12 are three flowcharts that exemplify respectivedifferent operating logics of the control system of the fan according tothe invention.

DETAILED DESCRIPTION OF THE INVENTION

With initial reference to FIG. 1, the variable-geometry fan according tothe invention, which can he used, for example, for cooling the lubricantof the internal-combustion engine of an industrial vehicle, comprises,in a way generally in itself known, a hub 1 provided for being governedin rotation with usual modalities and fitted on the periphery of whichis a ring of blades 2.

Each blade 2 is constituted by an elastically deformable bodyincorporating one or more laminas of a shape-memory alloy, generallyaccording to what is described and illustrated in the aforesaid Europeanpatent application No. EP-2078865A2.

In detail, each blade 2 is shaped with specific profiles appropriatelystudied with a view to maximizing the fluid-dynamic efficiency, andconsists in a matrix made of a thermosetting or thermoplastic polymericplate, possibly fibre-reinforced. The solution that appears currentlymost promising from the industrial standpoint envisages the use of athermoplastic material, for example, nylon, and injection-mouldingmanufacturing techniques. More in particular, each blade 2 can be madein the way represented schematically in FIG. 7, with two distincthalf-shells 3, 4 formed with respective channels 5, 6. The twohalf-shells 3, 4 are then fitted together permanently via fixed joints7, 8 (and/or gluing or else other equivalent systems) in such a way thatthe two channels 5, 6 are set facing one another so as to define aninternal duct 9. Said duct 9, the path of which can, for example, be theone represented schematically with a dashed line in FIG. 6, defines acircuit for circulation of a thermal fluid, which will be described inwhat follows.

With reference once again to FIG. 7, the hermetic seal of the duct 9 isguaranteed by gaskets 10, for example, made of silicone material,inserted in corresponding facing recesses of the two half shells 3, 4.

Set within the duct 9, along its entire path or more conveniently onlyin some stretches (for example, three in number as represented in FIG.6) are laminas 11 made of a shape-memory metal alloy. Typically, thelaminas 11 are made of an NiTi-based alloy, and are gripped between thehalf-shells 3, 4 along the middle of the channel 11. In this way, theopposite faces of each lamina 11 facing the channel 5 and the channel 6,respectively, in the way represented in FIG. 7, can be both lapped bythe thermal fluid circulating along the duct 9.

The duct 9 of each blade 2 is connected to a tubular connector 12, forexample, screwed on the periphery of the hub 1 and in communication witha radial manifold or distributor, designated as a whole by 13 in FIG. 2,set within the hub 1 itself.

The radial distributor 13 communicates with an inlet duct 14 and with anoutlet duct 15 set one inside another coaxially with respect to the hub1 and rotating together with it. As is illustrated in detail in FIGS. 4,5 and 8, the inlet duct 14 and the outlet duct 15 are rotatably fittedto respective stationary tubular connectors 16, 17 set radially withrespect to the hub and in turn communicating with a double hydrauliccircuit, represented schematically in FIG. 2 and designated as a wholeby 18.

The hermetic seal between each rotatable duct 14, 15 and thecorresponding stationary connector 16, 17 is obtained by means ofrespective annular flanges 19, 20 and 21, 22 in mutual sliding contact,it being possible for said contact to be direct (in the way representedin FIG. 8) or else envisage the use of annular sliding bearings 23, 24set between the flanges 19, 20 and 21, 22 (in the way represented inFIG. 9).

With reference now to FIG. 2, the double hydraulic circuit 18 includes afirst delivery line 25 and a first return line 26 for circulation, via apump 27, of a hot liquid coming from a reservoir 28, and a seconddelivery line 29 and a second return line 30 for circulation, via a pump31, of a cold liquid, coming from a reservoir 35.

The hot liquid and the cold liquid can be advantageously constituted bythe cooling liquid or glycol itself of the internal-combustion engine towhich the fan according to the invention is to be operativelyassociated. In particular, the hot liquid of the reservoir 28 mayconsist of a certain amount of cooling glycol drawn off prior to itsentry into the corresponding cooling radiator, whilst the cold liquid ofthe reservoir 35 may be the coolant itself leaving the radiator.Alternatively, the cold liquid may come from an autonomous circuitdistinct from that of the glycol for cooling the engine, as also the hotliquid may be supplied by an autonomous circuit.

Designated by 32 and 33 are two three-way solenoid valves that controlthe communication between the first delivery line 25 and the firstreturn line 26 on one side, and between the second delivery line 29 andthe second return line 30 on the other, with the stationary inlet duct16 and rotating inlet duct 14 and with the stationary outlet duct 17 androtating outlet duct 15 which are in turn connected, in the wayclarified previously, with the ducts 9 of the blades 2 incorporating theshape-memory laminas 11.

The solenoid valves 32, 33 are operatively connected to an electroniccontrol unit 34 that governs driving thereof, as a function of thetemperature of the engine lubricant exposed to the flow generated by thefan, according to different logics that can be selectively modifiedthrough programming thereof. For detecting the temperature of the enginelubricant a transducer of a conventional type is provided, notillustrated in the drawings, connected to the control unit 34.

Three examples of possible control logics will now be described withreference to the flowcharts of FIGS. 10, 11 and 12.

The control logic exemplified in FIG. 10 is of the on/off type: theactivation of the shape-memory laminas 11 is connected to the maximumdeformation attainable for a given arrangement of the laminasthemselves. The parameter that determines circulation of the hot/coldglycol is obviously the temperature of the lubricating oil detectedinside the engine. If the temperature detected exceeds an upperthreshold value (for example, 80° C.), set in the testing stage, theelectronic control unit 34 actuates the solenoid valves 32 and 33 so asto open the communication between the hot circuit (first delivery line25, first return line 26) and the ducts 9 of the blades 2, through theinlet ducts 16, 14 and the outlet ducts 15, 17. The glycol, which isalready at the temperature necessary to guarantee maximum deformation ofthe blade profile, thus circulates in the ducts 9. Once the temperatureof the lubricant has dropped to a lower threshold value, which also hasbeen set in the testing stage (for example, 75° C.), the control unit 34interrupts delivery of the hot liquid and opens the communicationbetween the circuit of the cold liquid (second delivery line 29, secondreturn line 30) and the ducts 9, until the blade geometry is broughtback into the initial configuration as a result of return of theshape-memory laminas 11 into the starting position. This is obtained ina taster and more efficient way than in the case of a natural, i.e.,non-forced, cooling of the laminas 11.

The deformation set will be equal to the maximum deformation attainable,in relation to the dimensions of the fan and for a given distribution ofthe shape-memory laminas 11 within each blade 2. Once these operatingparameters are fixed it is possible to define the temperature of the hotglycol capable of ensuring the maximum expected deformation.

The second control logic, implemented according to the flowchart of FIG.11, is instead of a modular type: in the testing stage, all thevariables that enable deformation of the blade profile to be broughtabout up to the required degree of deformation are determined. For agiven geometrical arrangement of the shape-memory laminas 11 the firstdecision regards the expected degree of deformation: this choice isstrictly linked to the performance curve of the fan and to the type ofthe engine to which it is associated. Once these three parameters havebeen set, it is possible to derive the point of operation of the systemand hence the temperature of the glycol that must be reached toguarantee the expected deformation. It follows, for example, that in thepresence of fans of modest dimensions the temperature of the glycolcapable of activating the shape-memory laminas 11 will be more containedthan in the case of fans of larger dimensions.

Also in this ease, activation of the shape-memory laminas 11 is governedas a function of the detected temperature of the engine lubricant.However, unlike the previous logic, it is possible to decide in thetesting stage the degree of deformation with which to operate. Thechoice of not exploiting the maximum deformation of the shape-memorylaminas 11, and hence of the blades 2, results in an energy savingderiving from a lower temperature of the incoming glycol, and in alonger fatigue life of the fan that is not used to the maximum of itspotential.

Also with the control logic defined by the flowchart of FIG. 11, theupper threshold temperature of the lubricant beyond which activation ofthe shape-memory laminas 11 occurs is assumed as being 80° C. and thelower threshold temperature 75° C.

The third control logic exemplified by the flowchart of FIG. 12 is alsoof a modular type, like the previous one, but the decisions duringtesting regard, in addition to the expected degree of deformation, alsothe time t₁ necessary for completing the deformation, and hence thereduction of the temperature of the oil. The cooling times are thenevaluated in relation to a safety parameter Δt, which is also set in thetesting stage. Once the performance curve of the fan and the type of theengine to which it is associated have been identified, as describedpreviously, it is possible to define the point of operation of thesystem and hence the temperature T_(G) of the glycol to be reached toguarantee the expected deformation.

-   -   a. Activation is always determined by measuring the temperature        of the engine lubricating oil, but the times fixed in the        testing stage enter into play. Consider, for reasons of        simplicity, a numerical example: t₁ is assumed as being 120 s,        and Δt 50 s, When the temperature of the oil detected is higher        than 80° C. assumed as upper limit value, circulation of the hot        glycol is activated.

Once a time shorter than t₁−Δt has elapsed, two conditions may present:

-   -   i. if the temperature of the oil has dropped below the maximum        value, it means that the deformation reached has already had the        effect of reducing the temperature, and it is thus possible to        activate the circuit of the cold glycol and thus complete the        cycle of activation;    -   ii. if the temperature of the oil is still higher than the        threshold value, given that there are once again 70 s available        for reducing the temperature, it is sufficient to prolong        circulation of the glycol at T_(G).

If instead, a time equal to or longer than t₁−Δt has elapsed and thetemperature of the glycol is still above the threshold of 75° C., aheater further heats the glycol above T_(G) in such a way as to increasethe level of deformation of the blade profile and enable return withinthe threshold value in the pre-set time.

In this way, it is possible to guarantee a modular deformation of theblade profile respecting the times set in the testing stage. It isimportant in this case to emphasize the advantages in terms of energysaving, thanks to the fact that the temperature of the glycol is broughtabove T_(G) only when necessary. Moreover, a longer working life of thefan is achieved since it is not used to the maximum of its potential.

Finally, this third control logic can be viewed in relation to thedifferent environmental conditions in which the fan will operate in use.For example, in the case of operation at low winter temperatures, theconditions could be such as not to require heating of the glycol to atemperature T>T_(G), thus limiting the power absorbed.

Of course, without prejudice to the principle of the invention, thedetails of construction and the embodiments may vary widely with respectto what is described and illustrated herein, without thereby departingfrom the scope of the invention as defined in the ensuing claims.

Thus, optimization of the temperatures of transformation of the NiTishape-memory laminas inserted within the blades can enable use of thehot fluid already present within the vehicle (glycol of the enginecooling system) for activation of the laminas themselves and consequentmodification of the blade profile. The hot glycol could be drawn offprior to its entry into the engine radiator and conveyed within theblades of the fan according to the modalities already indicated. At theend of the activation envisaged, cooler fluid will he conveyed into theblades to favour subsequent cooling of the laminas and thus accelerateand favour return of the blades into their initial configuration. Inrelation to the thermal sizing for the engine of the vehicle, for thecooling step colder glycol could be used by drawing it of at the outletfrom the radiator (if ΔT is sufficient) or by providing a dedicatedcircuit of cooler fluid. In this way, stagnation of hot fluid within theblades is avoided, and return to the initial configuration, which willbe facilitated by the convection effect of the flow of air thattraverses the fan, is favoured.

Moreover it may be contemplated, according to a different operatinglogic, that it is the temperature of the engine compartment, and henceof the air that traverses the fan, that determines optimal configurationof the geometry of the blades that is designed to enable the dueflowrate of cooling air. In this case, possibly envisaging that thelaminas are partially exposed and consequently lapped by, and in directcontact with, the air to improve heat exchange, it is possible to enablea progressive regulation of the geometry of the blades. Thefluid-heating and cooling circuits would no longer be necessary, but theconvection effect and the transition of crystalline phases that occur inthe laminas in relation to the temperature of the air would bring aboutcontinuous adaptation of the geometry of the blades to the requiredoperating conditions.

What is claimed is:
 1. A variable-geometry fan for cooling a lubricantof an internal-combustion engine, comprising: a rotating hub bearing aring of blades each having elastically deformable structureincorporating at least one lamina made of a shape-memory alloy, andcontrol means for applying thermal energy to said at least one lamina soas to vary the geometry of the blade, wherein said control means includea circuit for circulation of a thermal fluid through internal ducts ofeach blade.
 2. The fan according to claim 1, wherein said circuit forcirculation of a thermal fluid includes a first delivery line and afirst return line for a hot liquid, a second delivery line and a secondreturn line for a cold liquid, solenoid-valve means for opening andclosing the communication between said ducts and said first lines orsaid second lines, and an electronic control unit operatively connectedto said solenoid-valve means.
 3. The fan according to claim 2, whereinsaid electronic control unit is configured for driving opening andclosing of said solenoid-valve means as a function of the temperature ofthe engine lubricant.
 4. The fan according to claim 3, wherein saidelectronic control unit is configured for operating according toselectively modifiable logics.
 5. The fan according to claim 1, whereinsaid at least one shape-memory lamina is set along said internal ductsof the blade.
 6. The fan according to claim 5, wherein said at least oneshape-memory lamina is exposed in said internal duct on both of itsfaces.
 7. The fan according to claim 1, wherein the hub has a radialdistributor communicating with the internal ducts of the blades andconnected to an inlet duct and to an outlet duct of said thermal fluidset coaxially with respect to the hub.
 8. The fan according to claim 7,wherein said inlet and outlet ducts include respective rotatablesections turning with said hub and connected to respective stationarysections via sliding-seal connectors.
 9. The fan according to claim 8,wherein said sliding-seal connectors include annular sliding bearings.10. The fan according to claim 1, wherein each blade is formed by a pairof half-shells seal-fitted together and having respective channelsfacing one another to form said ducts.
 11. The fan according to claim 1,wherein said thermal fluid comprises coolant of the internal-combustionengine.
 12. A method for controlling the geometry of the blades of avariable-geometry fan for cooling a lubricant of an internal-combustionengine, in which said blades have an elastically deformable structureincorporating laminas made of a shape-memory alloy to which thermalenergy is applied, wherein application of the thermal energy comprisescirculating a thermal fluid through internal ducts of each blade, towhich ducts said laminas are exposed.
 13. The method according to claim12, wherein the thermal fluid includes a hot liquid and a cold liquid,and further comprising controlling circulation of the fluid through saidinternal ducts as a function of the temperature of the lubricant of theengine to which the fan is applied.
 14. The method according to claim12, wherein said thermal fluid comprises a coolant of theinternal-combustion engine to which the fan is applied.